The present invention generally relates to brake fluid pressure control and more particularly, to a brake fluid pressure control device which is capable of performing traction control by adding a simple arrangement to a brake fluid control device for antiskid control.
Conventionally, a brake fluid pressure control device has been provided which is capable of performing not only antiskid control but traction control by adding devices to a brake fluid pressure control device for antiskid control. For example, such a brake fluid pressure control device is proposed in Japanese Utility Model Laid-Open Publication No. 4-57476 (1992) as shown in FIG. 6. In the known brake fluid pressure control device of FIG. 6, so-called X-shaped piping is employed. Thus, a wheel cylinder 4A for a front left driving wheel 3A and a wheel cylinder 4B for a rear right driven wheel 3B are connected with a pipe line 2A communicating with a master cylinder 1, while a wheel cylinder 4C for a front right driving wheel 3C and a wheel cylinder 4D for a rear left driven wheel 3D are connected with a pipe line 2B communicating with the master cylinder 1.
Namely, the master cylinder 1 is connected with the wheel cylinders 4A and 4C for the front left and right wheels 3A and 3C through the pipe lines 2A and 2B, three port connection and two position solenoid valves 6A and 6B and three port connection and three position solenoid valves 7A and 7B, respectively. Meanwhile, the wheel cylinders 4B and 4D for the rear right and left wheels 3B and 3B are connected, via three port connection and three position solenoid valves 9A and 9B, with pipe lines 8A and 8B branched from the pipe lines 2A and 2B, respectively.
Meanwhile, in the known brake fluid pressure control device, the front left wheel 3A and the rear right wheel 3B are connected with a reservoir 11A by way of the solenoid valves 7A and 9A, respectively, while the front right wheel 3C and the rear left wheel 3D are connected with a reservoir 11B through the solenoid valves 7B and 9B, respectively. Suction sides 12a of pumps 12A and 12B are, respectively, connected with the reservoirs 11A and 11B, while discharge sides 12b of the pumps 12A and 12B are, respectively, connected with the pipe lines 2A and 2B. The pumps 12A and 12B are further connected, via the solenoid valves 7A and 7B, with the wheel cylinders 4A and 4C for the front left and right wheels 3A and 3C, respectively. Furthermore, a reservoir la of the master cylinder 1 is connected with the reservoir 11B by a pipe line 13 provided with an on-off type solenoid valve 14.
At the time of ordinary braking of the known brake fluid pressure control device, fluid pressure of the master cylinder 1 is supplied to the wheel cylinders 4A and 4C for the front left and right wheels 3A and 3C through the pipe lines 2A and 2B, the solenoid valves 6A and 6B set to a shown position A and the solenoid valves 7A and 7B set to a shown position C, respectively and is also supplied from the pipe lines 8A and 8B to the rear right and left wheels 3B and 3D via the solenoid valves 9A and 9B set to a shown position F.
On the other hand, at the time of antiskid control of the known brake fluid pressure control device, working fluid in the wheel cylinders 3A to 3D is discharged from the solenoid valves 7A and 7B set to a position E and the solenoid valves 9A and 9B set to a position G to the reservoirs 11A and 11B through pipe lines 15A and 15B so as to perform pressure reduction. The working fluid in the reservoirs 11A and 11B is pumped up by the pumps 12A and 12B so as to be returned to the master cylinder 1 through the solenoid valves 6A and 6B set to the position A.
Furthermore, at the time of traction control of the known brake fluid pressure control device, the solenoid valve 14 is set to an open state so as to actuate the pump 12B. Thus, working fluid in the reservoir 1a is supplied to the wheel cylinder 4C for the front right driving wheel 3C through the pipe line 13, the pump 12A and the solenoid valve 7B set to the position C or is supplied from the discharge side 12b of the pump 12B to the wheel cylinder 4A for the front left wheel 3A by way of the solenoid valves 6A and 6B set to a position B and the solenoid valve 7A set to the position C.
In the known brake fluid pressure control device, the pipe line 13 for connecting the master cylinder 1 and the reservoir 11B is required to be provided for pressurizing at the time of traction control. Generally, in the brake fluid pressure control device of this kind, the solenoid valves 6, 7, 9 and 14, the pumps 12, etc. are formed of one module and the module is disposed at a position relatively distant from the master cylinder 1 in a motor vehicle. Therefore, the pipe line 13 becomes long necessarily and structure of the brake fluid pressure control device becomes complicated. Furthermore, flow resistance of the pipe line is large when the working fluid in the reservoir 1a is sucked by the pump 12B, which is not preferable for power efficiency of the pumps.
In addition, in the known brake fluid pressure control device, since the solenoid valve 14 should be provided in the pipe line 13 so as to connect the reservoirs 1a and 11B only at the time of traction control. Accordingly, the number of the components of the known brake fluid pressure control device is increased and structure of the known brake fluid pressure control device becomes complicated.